The Court of Appeal has rejected a bid for home detention by a Catholic brother convicted of the historical sexual abuse of disabled boys in his care.

Brother Rodger William Moloney appealed against the two years and nine months prison term he was given at the High Court in Christchurch in August last year.

In June, Moloney was convicted on seven charges involving sexual offending in the 1970s at Marylands School in Christchurch. The school was operated by the Order of St John of God, of which Moloney was then prior.

Moloney's lawyer, Greg King, told the Court of Appeal that when Moloney was sentenced it was believed 10 years was the maximum sentence for his offending against boys aged 12 to 16. It was now agreed the maximum was seven years.

"Had the correct maximum sentence ... at the time been known to the judge, that may have reduced the penalties imposed, perhaps to the point where a sentence of home detention might have been realistically considered as an alternative to imprisonment," King said.

Moloney had no previous convictions, 30 years had passed since the offending and, at 73, Moloney was in ill health and at low risk of reoffending.

The Crown argued that home detention was an inappropriate sentence, given the number of victims, their disability, the abuse of trust involved in the offending and the impact on the complainants.

In its ruling, issued yesterday, the Court of Appeal agreed home detention was both inappropriate and unavailable."The offending for which the appellant was convicted was, on any measure, serious offending of its type," the court ruled.

"It persisted over a lengthy period and involved boys or young men who suffered disabilities and were necessarily subservient to the wishes of the appellant ... Overt or inherent coercion was a feature of the offending."

Moloney's offending had a major impact on the complainants that had persisted for decades, the court said.